IEEE (and Electronics Engineers) 802.16e standards have been adapted in the name of ‘WMAN-OFDMA TDD’ as sixth standards for IMT (International Mobile Telecommunication)-2000 in ITU (International Telecommunication Union-affiliated ITU-R (ITU-Radio communication sector) in 2007. ITU-R is preparing an IMT-Advanced system as next-generation 4G mobile communication standards after IMT-2000. IEEE 802.16 WG (Working Group) determined to promote an 802.16m project to aim at creating amendment standards of the existing IEEE 802.16e, as standards for the IMT-Advanced system in late 2006. IEEE 802.16m standards are required to satisfy the advanced requirements for the IMT-Advanced system while maintaining the compatibility with the 802.16e standard-based Mobile WiMAX system.
A next-generation wireless communication system may support a multi-carrier mode. The multi-carrier mode refers to a mode supporting a plurality of carriers for a single mobile station (MS) to allow for broadband communication. The conventional wireless communication system supports only a single carrier. In the multi-carrier mode, each carrier is designed to meet basic requirements of operating an independent system. That is, each independently operable band in the multi-carrier mode can be defined as a carrier.
The next-generation wireless communication system such as 3GPP LTE-A or IEEE 802.16m supports broadband by aggregating one or more carriers to extend bandwidth up to 20 MHz or greater. For example, when a single carrier corresponds to a bandwidth of 5 MHz, four carriers are aggregated to support a maximum 20 MHz bandwidth. In this manner, a plurality of carriers may be used in the multi-carrier mode.
Meanwhile, the MS can transmit feedback information to a base station (BS) via uplink. Feedback of the MS may be performed according to a BS request or may be driven by an event. According to the conventional standard (e.g., IEEE 802.16m D7), the BS transmits a control message for requesting feedback to the MS through a downlink carrier. Then, the MS transmits the feedback information to the BS through an uplink carrier linked to the downlink carrier. In this respect, according to the conventional standard, the BS should transmit the control message only through a particular downlink carrier. This scheme may not cause a problem in a system using a single carrier, but may be problematic in a system using multiple carriers. That is, to which of carriers the control message transmitted through the particular downlink carrier is related is unclear.
Also, according to the conventional standard, it is stipulated that feedback information should be transmitted only through a particular carrier in driving the feedback of the MS through an event. Thus, in the multi-carrier mode, to which of carriers the feedback information is related is unclear.
Therefore, a method and apparatus for transmitting feedback information of the MS in the wireless communication system supporting the multi-carrier mode are required.